In recent years, hydrogen has been drawing attention as a clean energy. As a process for obtaining such hydrogen, there is known a reforming reaction for the hydrocarbon contained in gasoline, kerosene, gas oil or the like. However, a high temperature of 700 to 900° C. is generally required in the reforming reaction of the hydrocarbon contained in gasoline or the like; therefore, a large reforming apparatus is needed and, moreover, a large starting energy and a long starting time are required in order to advance the reforming reaction. Hence, there is being investigated a technique of applying a pulse voltage or the like to a pair of electrodes to generate a plasma and utilizing the plasma to conduct a reforming reaction at a low temperature at a high efficiency.
There is, for example, a proposal on a plasma fuel converter in which glow discharge is generated between a pair of electrodes and the plasma generated by the glow discharge is utilized to convert a fuel (see Patent Document 1).
There is also a proposal on a method and apparatus in which pulse discharge is conducted in a mixed gas (a to-be-reformed gas) of alcohol and steam to generate a plasma and a reforming reaction of the mixed gas is conducted using the plasma, to generate hydrogen (see Patent Document 2).
There is further a proposal on a reformer in which a pair of electrodes are placed inside the cells of a honeycomb structure made of an insulating material (e.g. cordierite), discharge is conducted inside the cells to generate a plasma, and a reforming reaction is conducted using the plasma (see Patent Document 3).
The plasma fuel converter, etc. described in the Patent Documents 1 to 3, as compared with the conventional art, have an advantage that the reforming of hydrocarbon can be carried out at a relatively low cost under the mild conditions of low temperature and normal pressure. However, they have not been fully satisfactory in the reaction efficiency of reforming reaction.
Hence, it is being attempted to promote the reforming reaction and enhance the reaction efficiency of reforming reaction by, in conducting a reforming reaction using a plasma, using further a catalyst for promotion of reforming reaction. In this case, the reforming reaction is considered to proceed synergistically by the action of plasma and the action of catalyst.
There is, for example, a proposal on a hydrocarbon reforming apparatus which have a gas-mixing vessel for mixing a hydrocarbon and steam, a power source and a pair of electrodes present inside the gas-mixing vessel and wherein a voltage of particular pulse frequency is applied to the pair of electrodes to generate a plasma and a conversion reaction into hydrogen is conducted using the plasma (see Patent Document 4). The Patent Document 4 describes that the conversion reaction can be promoted by filling a particulate catalyst inside the gas-mixing vessel (a so-called packed bed method).
There is also a proposal on a fuel reforming apparatus which has a reactor, a pair of needle-like electrodes disposed inside the reactor so as to face each other, a device for voltage application, a particulate oxide catalyst, and a catalyst-holding means for holding the oxide catalyst in the reactor (see Patent Document 5).                Patent Document 1: National Publication of International Patent Application No. 2003-514166        Patent Document 2: JP-A-2003-73103        Patent Document 3: JP-A-2006-248847        Patent Document 4: JP-A-2004-345879        Patent Document 5: JP-A-2006-56748        